RENAL RESPONSE TO HEMODILUTION WITH ALBUMIN OR CROSS-LINKED BOVINE HEMOGLOBIN - ROLE OF NITRIC-OXIDE

The decreased hematocrit that occurs with hemodilution leads to a decr ease in peripheral resistance while venous return and cardiac output i ncrease, We determined systemic and renal responses to hemodilution wi th a solution of albumin or a crosslinked hemoglobin-based oxygen carr ier (XLHb) and the effect of inhibition of NO synthesis on the respons es to albumin, Clearance experiments were done on anesthetized rats to determine mean arterial pressure (MAP), glomerular filtration rate (G FR), effective renal plasma flow (ERPF), and sodium excretion before a nd after isovolemic exchange transfusion (2 ml per 100 gm body weight) with either(1) 5% albumin (n = 5), (2) 5% albumin plus N-omega-nitro- L-arginine methyl ester (L-NAME, 3.5 mg/kg; n = 6), or (3) 6% XLHb (n = 7) and after administration of L-NAME alone (n = 4), Hematocrit decr eased similarly in all exchange groups (from 42 +/- 1.0 to 29 +/- 1.3) , MAP decreased with albumin exchange, increased with L-NAME, and rema ined unchanged with albumin+L-NAME or XLHb. GFR, ERPF, and renal blood flow increased while filtration fraction and renal resistance decreas ed with albumin exchange; responses were the opposite with L-NAME, and with albumin+L-NAME and XLHb these parameters remained approximately the same as control values, Red cell delivery decreased with L-NAME, a lbumin+L-NAME, and XLHb but remained at control levels with albumin, I n conclusion, renal effects of decreased hematocrit can be offset by d ecreased NO availability, The similarity of results with XLHb and albu min+L-NAME is consistent with NO scavenging by hemoglobin. Increased r enal vascular tone with XLHb limits oxygen delivery.